The present invention relates to valve stems, their constructions, and methods of manufacturing them. It more particularly relates to the construction of valve stems used in gate valves.
Valve stems are typically made of copper based alloys machined from bar stock, castings or forgings. The finished valve stem typically includes a coarse square (acme style) thread, a thrust ring, and a flattened transition to accept a handwheel or wrench, and a standard threaded end for accepting a retaining nut thereon. A number of machining steps are required to produce the finished valve stem. The prior art manufacturing methods are thus equipment and labor intensive and accordingly expensive.
Many types of valve stems are known, and examples thereof are shown in the following U.S. patents:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 1,209,145 Grabill 1,483,631 Forbes 1,954,643 Neuhaus 2,842,336 Johnson 4,243,070 Jackson 4,512,550 Kocher 4,527,771 Yeary 4,532,957 Battle 4,541,608 Forester 4,621,790 Balter 4,658,848 Meyer 4,660,591 Brown 4,705,062 Baker ______________________________________
(Each of these patents and any other publications mentioned herein are hereby incorporated by reference in their entireties.) As will be apparent, the present invention can be adapted to form generally any of the valve stem configurations disclosed in these patents.